She’s still around and touring. Maybe you’re thinking of Laura Nyro.
He had started out as a teenager in 1968 with his sister Sally as a vocal folk duo with one UK hit, but now he was on his own, writing pieces for orchestra. This belongs to a genre known as Minimalism, which uses repeated fragments, sometimes harmonized and sometimes worked as counterpoint.
This little number in A minor is an excerpt from a much longer piece. Director William Friedkin used it in The Exorcist, the film that sent terrified moviegoers to the nearest Catholic church. It was an inspired decision on Friedkins part because the repeated fragments sound like a lost soul trapped and circling without a sense of where it is or how to get out. Its a haunting number, and people who had seen the movie would get cold chills just listening to it years later.
Oops...maybe so. I just knew it was someone who had one big hit and then died before she had a chance to have more.